The fire at a controversial Auckland mosque started in a shed at the back of the building.

Emergency services were called to the Islamic Centre in Avondale in the early hours of this morning, with fire and police investigators now looking into the cause.

Detective Senior Sergeant Paul Newman says the fire started in a storage area attached to the side of the building, and the mosque itself escaped damage.

Police aren't commenting on possible causes.

The centre has hit the news before, over conflicting claims of a radical element.